532 bulletin: museum of comparative zoology. 



Specimens examined. — Twenty-seven skulls from Unalaska, viz., 

 the type and 25 others in the U. S. Biological Survey collection, and 

 a nearly perfect skull in the U. S. N. M. 



DiCROSTONYX EXSUL, sp. nOV. 



St. Lawrence Island Lemming. 



Cuniculatus torquatus Nelson, Rept. nat. hist, collections in Alaska, 1887, 

 p. 278 (part). 



Type. — Skin and skull. Adult cf, M. C. Z. 11,885, St. Lawrence 

 Island, Bering Sea, 24 June, 1913. Joseph Dixon. 



General characters. — Similar to ruhricatus but coloring much less 

 intense, more grayish throughout. Skull with more abruptly nar- 

 rowed nasals, their proximal ends bevelled sharply to a median point 

 instead of tapering gradually; interparietal more nearly square in 

 general outline. 



Color. — The type has nearly clear gray cheeks, but slightly mixed 

 with black hairs ; nose and area between the eyes gray, much darkened 

 by black hairs; indistinct blackish median line on the back, not clear 

 black as in ruhricatus; ear-patch a mixture of ochraceous-buff and 

 tawny; rest of the upper parts a general pinkish gray, blacker on the 

 rump, due to a slight admixture of black hairs with others having 

 concealed slaty bases, a broad whitish subterminal band, and a fer- 

 ruginous tip. At the sides of the body the black hairs are wanting, 

 and the whitish ring of the other sort of hairs is broader and clearer, 

 the colored tip longer and yellower, nearly orange-buff, most intense 

 at the shoulders. Chin and under sides of fore legs clear white, 

 throat heavily washed with tawny, which blends into the ochraceous- 

 buff wash of the rest of the under parts. Tail whitish; feet pale buff 

 above in their central portion, whitish with a dusky tinge peripherally. 



Skull. — The skull is very similar to that of D. ruhricatus of the 

 Alaskan mainland, but the nasals are more abruptly narrowed at 

 about their distal two thirds; thence they taper slightly toward the 

 proximal end, where each is bevelled at an angle of about 45 degrees, 

 to a median point. In ruhricaius the taper is much more gradual 

 from anterior to posterior end, and the bases are usually but slightly 

 or not bevelled. The interparietal, in the specimens examined, is 

 more nearly square, hence of less transverse width than in ruhricatus 

 (Plate, 1, fig. 9). The teeth show no important differences. 



